Nitrate source apportionment in the complex Nyando tropical river basin in Kenya

 

27th December, 2020

Journal of Hydrology

 

 

Abstract

Excess nitrate (NO3−) discharge into fresh water resources poses detrimental effects on ecosystems and human health, yet the understanding of its potential sources is lacking in many parts of Sub-Saharan Africa. This study integrated hydrochemistry, multi-isotope tracers (δ15N-NO3−, δ18O-NO3−, δ11B) and a Bayesian mixing model (mixSIAR) to improve on the apportionment of multiple NO3− sources in the Nyando River basin of Lake Victoria, Kenya. River water was monitored spatially in the basin for hydro-chemical and isotopic parameters from July 2016 to May 2018. The data shows that NO3− concentrations in the basin are governed by the predominant land use. Mixed agriculture (MA) land use recorded significantly higher NO3− concentrations (8.8 ± 10.6 mg L−1), compared to other land use zones: residential & industrial (RI) 3.4 ± 2.2 mg L−1, sugarcane (S) 3.2 ± 1.5 mg L−1 and tea & forest areas (TF) 3.0 ± 1.1 mg L−1.

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